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I'm implementing a basic digraph with weighted edges for street routing in a small geo area (600mx600m). How and where can I get the required data to populate such a structure? I've been reading about OpenStreetMap, but am unsure as to how I can export the required data into my application.

The kind of data I would need is - all the streets (nodes) in the specified area, their connecting streets (subsequent nodes), and the distances between them.

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Does it have to be a JAVA-only solution? –  underdark May 13 '12 at 11:10
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2 Answers

My bad. If you know Python, here's a code snippet that imports osm data and convert's it to a NetworkX graph:

Read graphs in Open Street Maps osm format

Based on osm.py from brianw's osmgeocode
http://github.com/brianw/osmgeocode, which is based on osm.py from
comes from Graphserver:
http://github.com/bmander/graphserver/tree/master and is copyright (c)
2007, Brandon Martin-Anderson under the BSD License

import xml.sax
import copy
import networkx

def download_osm(left,bottom,right,top):
    """ Return a filehandle to the downloaded data."""
    from urllib import urlopen
    fp = urlopen( "http://api.openstreetmap.org/api/0.5/map?bbox=%f,%f,%f,%f"%(left,bottom,right,top) )
    return fp

def read_osm(filename_or_stream, only_roads=True):
    """Read graph in OSM format from file specified by name or by stream object.

    filename_or_stream : filename or stream object

    G : Graph

    >>> G=nx.read_osm(nx.download_osm(-122.33,47.60,-122.31,47.61))
    >>> plot([G.node[n]['data'].lat for n in G], [G.node[n]['data'].lon for n in G], ',')

    osm = OSM(filename_or_stream)
    G = networkx.Graph()

    for w in osm.ways.itervalues():
        if only_roads and 'highway' not in w.tags:
        G.add_path(w.nds, id=w.id, data=w)
    for n_id in G.nodes_iter():
        n = osm.nodes[n_id]
        G.node[n_id] = dict(data=n)
    return G

class Node:
    def __init__(self, id, lon, lat):
        self.id = id
        self.lon = lon
        self.lat = lat
        self.tags = {}

class Way:
    def __init__(self, id, osm):
        self.osm = osm
        self.id = id
        self.nds = []
        self.tags = {}

    def split(self, dividers):
        # slice the node-array using this nifty recursive function
        def slice_array(ar, dividers):
            for i in range(1,len(ar)-1):
                if dividers[ar[i]]>1:
                    #print "slice at %s"%ar[i]
                    left = ar[:i+1]
                    right = ar[i:]

                    rightsliced = slice_array(right, dividers)

                    return [left]+rightsliced
            return [ar]

        slices = slice_array(self.nds, dividers)

        # create a way object for each node-array slice
        ret = []
        for slice in slices:
            littleway = copy.copy( self )
            littleway.id += "-%d"%i
            littleway.nds = slice
            ret.append( littleway )
            i += 1

        return ret

class OSM:
    def __init__(self, filename_or_stream):
        """ File can be either a filename or stream/file object."""
        nodes = {}
        ways = {}

        superself = self

        class OSMHandler(xml.sax.ContentHandler):
            def setDocumentLocator(self,loc):

            def startDocument(self):

            def endDocument(self):

            def startElement(self, name, attrs):
                if name=='node':
                    self.currElem = Node(attrs['id'], float(attrs['lon']), float(attrs['lat']))
                elif name=='way':
                    self.currElem = Way(attrs['id'], superself)
                elif name=='tag':
                    self.currElem.tags[attrs['k']] = attrs['v']
                elif name=='nd':
                    self.currElem.nds.append( attrs['ref'] )

            def endElement(self,name):
                if name=='node':
                    nodes[self.currElem.id] = self.currElem
                elif name=='way':
                    ways[self.currElem.id] = self.currElem

            def characters(self, chars):

        xml.sax.parse(filename_or_stream, OSMHandler)

        self.nodes = nodes
        self.ways = ways

        #count times each node is used
        node_histogram = dict.fromkeys( self.nodes.keys(), 0 )
        for way in self.ways.values():
            if len(way.nds) < 2:       #if a way has only one node, delete it out of the osm collection
                del self.ways[way.id]
                for node in way.nds:
                    node_histogram[node] += 1

        #use that histogram to split all ways, replacing the member set of ways
        new_ways = {}
        for id, way in self.ways.iteritems():
            split_ways = way.split(node_histogram)
            for split_way in split_ways:
                new_ways[split_way.id] = split_way
        self.ways = new_ways


Code's not mine btw.

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how can this help me load the data I need into my application? I can see that I can convert OSM to net files; how can I export route information that I can use? –  wulfgar.pro Mar 14 '12 at 2:48
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If you opted for a PostGIS/pgrouting based solution, you could import OSM data via osm2pgrouting : http://www.pgrouting.org/docs/tools/osm2pgrouting.html.

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